If you don't want to pay high prices, you need to have a map in front of you when you try to figure out where an airline does or doesn't fly.

Because driving an hour or two to get to a Southwest airport will usually save you LOTS of money compared to using an airline which flies directly to an airport where there's no low-fare competition.

Now, in your case, Springfield is SEVERAL hours from the nearest Southwest Airports (such as Kansas City or St Louis), so that might be far enough to not be worth it, especially given that that's your home base. But in the case of Richmond, I would suggest that Norfolk (where Southwest does fly to) is a more reasonable alternative to Richmond (especially if that's only one of the cities you'd fly to). And, btw, Southwest has in the past been in talks with Richmond about starting operations there in the future, but that was just before 9/11, and I have no idea if/when they might actually start flying there. But at any rate, Richmond vs Norfolk is not an issue if you're not willing to drive to a Southwest city from Springfield.

And if so, that brings up the next point: You should find which airlines serve Springfield (as well as any other airport[s] you DO consider close enough), and narrow your list to those (and their full partners). Then look at each of those and see whether they (at worst with transfers involving their partners) fly to the places you're most likely to want to fly. Chances are, for example, half of them won't fly to Richmond.

Oh, and regarding the rates from Springfield vs Kansas City or St Louis: It's called "the Southwest effect". Basically, even if YOU don't fly Southwest, the airports at which Southwest operates force the other carries to lower prices to compete with it. (There's a couple other strong discount carriers which have a similar effect.) But at smaller airports not served by any discount airlines, the airlines charge what the market will bear, which ends up of course being a lot higher.